1. Field of the Invention
The present invention relates to a solid-state image sensing device for images of long-wavelength light represented by the terahertz band, and specifically to a solid-state image sensing device having high sensitivity and high resolution, a method for the fabrication thereof, and an imaging system.
2. Related Art
There has been an infrared sensor that absorbs incident far-infrared lights (of a wavelength of 8 μm to 12 μm) in a cell unit to once convert into heat energy, which is in turn converted into electric signals by a thermoelectric conversion element provided in the cell unit (for example, refer to JP-A 2001-281065 (KOKAI)). However, by this configuration, frequency bands that spans between 100 GHz and 10 THz (wavelengths of 30 μm and 3 mm) having wavelengths longer than far-infrared lights and the characteristics of both electric wave and light, i.e., high-frequency long-wavelength electromagnetic waves represented by the terahertz band cannot be detected.
U.S. Pat. No. 6,441,368 adopts a system wherein an antenna structure is installed on an infrared sensor to receive electromagnetic waves of millimeter waveband from 30 GHz to 1 THz, and heat generated in the antenna is converted into electric signals by a thermoelectric conversion element. For the antenna structure, a protective pad is provided in the location facing the direction of incident electromagnetic waves, and thereby, the incidence of infrared lights (of a wavelength from about 1 μm to 30 m) having a higher frequency (shorter wavelength) than the above-described wavelength band into the detected cell is prevented. This is because the electromagnetic waves of the infrared band, which are constantly radiated from substances at normal temperature has an extremely high power compared with the power of the electromagnetic waves of the above-described millimeter waveband, and since the amount of radiation energy fluctuates, the electromagnetic waves of the infrared band must be blocked to constitute a detecting element specialized for millimeter waveband or terahertz band.
However, the protective pad structure disclosed in U.S. Pat. No. 6,441,368 has essential defects that: (1) the radiation from the protective pad itself cannot be ignored; (2) the protective pat absorbs millimeter waves or terahertz waves to be detected; and (3) capacity coupling occurs between the protective pad and the antenna structure to deteriorate antenna characteristics.